Method and apparatus for digital synthesis of microwaves through balanced transmission line structures

ABSTRACT

Conductor segments are positioned within a transmission line structure in order to generate microwave pulses. The conductor segments are switchably coupled to one or the other of the transmission lines or to each other, in parallel with the transmission line structure. Microwave pulses will be induced in the transmission line by closing the switches in a controlled manner to discharge successive segments or successive groups of segments into the transmission lines. The induced waves travel uninterrupted along the transmission lines in a desired direction.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for generatingmicrowaves and more particularly to a microwave source and a method forgenerating microwaves by digital synthesis.

BACKGROUND OF THE INVENTION

Digital synthesis of microwaves uses transmission lines and switches togenerate a series of alternating polarity pulses. The coupling of theresulting pulse train to a load such as an antenna results in theradiation of a short microwave pulse. This approach has beeninvestigated for over 30 years.

The general concept of producing microwaves by a sequential operation ofswitches is well known. High peak power microwave generation isaddressed by Driver et al. in U.S. Pat. No. 4,176,295 in which thegeneration of microwaves by periodically discharging a plurality ofidentical, direct current energized, resonant transmission lines into aTE wave guide at half-multiple wavelength spacings is discussed. Toperiodically discharge the transmission lines, each line is providedwith a switch, and all switches are simultaneously operated to cause theelectromagnetic energy in the waveguide to propagate as a pulse train ofmicrowave energy.

Mourou, in U.S. Pat. No. 4,329,686 discusses an arrangement, similar tothat of Driver et al., which uses a TE waveguide and a light activatedsolid state (LASS) switch for generating microwave pulses of picosecondduration, synchronously and in response to laser light pulses.

Unfortunately, the arrangements described by Driver et al. and Mourou donot produce clean microwave pulses and are limited in power since TEwaveguides have impedances close to that of free space, typically 50ohms or more, and therefore cause the LASS switches to operate outsidethe electric field and current density limits consistent with good highpower design principles, specifically, unidirectional power flow in acontinuously matched system.

Zucker, in “Light Activated Semiconductor Switches,” UCRL Preprint,October 1977 discusses the use of a light-activated semiconductorswitch, the basic principle of which is to create carriers in situ, thusobviating the need for diffusing the carriers necessary to transition atransistor or thyristor switch from a reversed biased (OFF) condition toa foreward biased (ON) condition. Zucker discusses the use of a laserbeam whose frequency is matched to the switching device band gap (1.09eV for silicon) to turn ON a LASS switch in less than 1 ps. As discussedin the article, a switch having sub nanosecond turn on time, and capableof being turned off after current ceases to flow, would be required formicrowave generation in order to allow for quick recharge and refire andfor the establishment of coherence among independent microwave sources.

Such a switch is addressed by Proud et al. in their article “HighFrequency Waveform Generation Using Optoelectronic Switching in Silicon”IEEE Trans on Microwave Theory and Techniques, Vol. MTT-26, No. 3(1978), in which the conversion of dc energy into RF pulses by using anarray of silicon switches simultaneously activated by a laser pulse isdiscussed. Proud et al. describe a “frozen wave” generator comprisingarrays of high-resistivity silicon switches fired by a gas laserdesigned to simultaneously fire all of the switches in synchronism. BothZucker and Proud techniques are represented by FIG. 1, which discloses agroup of transmission lines connected together by switches. In Zucker,the switches are activated sequentially, which gives flexibility inresulting wave shape, while in Proud the switches are activatedsimultaneously and produce frozen wave pulses. In both, the switchesremain in the ON state during the transmission of the entire pulse trainthrough the closed switches.

Mourou et al. in their article entitled “Picosecond Microwave PulseGeneration”, Appl. Phys. Lett. 38(6) (1981) discuss the generation of amicrowave burst in picosecond synchronization with an optical pulseusing a LASS switch coupled to an x-band waveguide and describe theefforts of others to generate microwave pulses using electrically drivenspark gaps and frozen wave pulses.

In U.S. Pat. Nos. 5,109,203 and 5,185,586, Zucker et al. teach:

(1) Sequential switching of two or more cascaded TEM transmission linesof arbitrary lengths, each transmission line being charged to anarbitrary voltage where the delay between any two switching events isequal or greater than the temporal length of the transmission lineseparating them with the first switch activated (closed) being the oneclosest to the load.

(2) The use of an optimized transmission line and switch geometry toyield the highest possible power flow.

(3) A “folded” microwave source configuration to provide addedcompactness and simplified energizing of the transmission lines.

(4) The use of reverse biased light activated solid state diodes asswitches to provide for extremely rapid switch recovery upon rechargingof the transmission lines after discharge, the recharging operating toforcefully reverse bias the diodes.

Despite the above advantages, the implementation of a transmission lineas a series of segments coupled together by switches causes problemswhen trying to provide a number of pulses in series. This is becauseeach pulse within sequential switching systems or frozen wave systemstravels through several closed switches implemented in series.Therefore, the signal level attenuates as the signal propagates througheach closed switch due to the residual resistance of each closed switch.Thus, sequential switching systems are not desirable for certainapplications because of attenuation problems and are limited by a lownumber of pulses.

A circuit called a Blumeline generator (U.K. Patent N/5 89127, 1941),depicted in FIG. 1B, has been used and based on a voltage inversionprinciple to generate power. The Blumeline generator operates using twoidentical two conductor lines. They can be incorporated in a singlethree conductor transmission line. In the latest version, the centralconductor is charged to a voltage (V) relative to each of the outer twoconductors. A single switch connects the central conductor to one of theouter conductors. When the switch is closed, the voltage on the switchedline is inverted and, after a time equal to the delay of this line, bothlines start to discharge to a load, converting the full stored potentialenergy into power on the load during double transit time of the line.

The Blumeline generators may be implemented in a stacked configuration(for increasing power) to enable the conversion of power from more thantwo transmission line segments. This is shown in FIG. 1C as one of theoptions for two stacked Blumeline generators. The stacked Blumelinegenerators, like the conventional Blumeline generator, generate a singleunipolar pulse when the switches are closed (at the same time) thatdrives the load after the equal time delay of each line. Neither theBlumeline generator nor the stacked one, however, has been used fordigital synthesis or to generate microwave signals in a series ofbipolar pulses on the common load.

There remains a need for a system that generates pulses with a highpulse rate. There remains a further need for a system that generates alonger series of pulses, that do not suffer significant attenuation witheach successive pulse. There remains a further need for such a system tobe implemented with switches that exhibit short rise time and jitter,and high switch power with or without low ON resistance.

SUMMARY OF THE INVENTION

According to the present invention, conductor segments (transmissionline conductors) are positioned within a transmission line structure inorder to generate microwave pulses. The conductor segments areswitchably coupled to one or the other conductor of the transmissionlines, in parallel with the transmission line structure. Microwavepulses may be induced in the transmission line by closing the switchesin a controlled manner to discharge successive segments, or successivegroups of segments, into the transmission lines. The induced pulsestravel uninterrupted along the transmission lines in a desired directionto the load.

Unlike the prior art, because the switches are positioned in parallelwith the transmission line structure, microwave pulses are induced intouninterrupted transmission lines which carry the signal in a desireddirection with only parallel connected opened swtiches. Because thesignal does not have to propagate through more than one closed switch,more pulses may be synthesized in a pulse train and the pulse train doesnot suffer unwanted attenuation associated with prior art digitalsynthesis techniques. The arrangement is susceptible to multipleimplementations and for longer microwave pulses.

For example, according to one embodiment of the invention, eachconductor segment may be charged to a different polarity and/or voltageas compared to the conductor segment on either side of it. In thisimplementation, all of the conductive segments are coupled throughswitches to one of the transmission line conductors. In thisarrangement, the switches may be closed by any stimulation technique toproduce a pulse train. According to one embodiment, the apparatusfunctions by sequentially activating switches from back to front alongthe pairs of transmission lines, thereby discharging the segments (eachcharged to a selected voltage) in series into the continuoustransmission lines. Appropriate timing of the closing of the switches isused to create a microwave signal having high power and high frequency.Because the switches are placed in parallel with the transmission line,lower quality switches may be used. Higher quality switches, such asLASS switches, may be used to give higher power and precise control ofthe signal and to allow coherence between multiple such sources tofacilitate the creation of a phased array system. The power of the pulsegenerated by such a system may be high, for example a 100 kV 50 ohmsystem may produce a 50 MW pulse. A 10 kV, 0.1 ohm system may produce a250 MW pulse. An adiabatic transformer may be used to provide couplingto an antenna. In principle, the system is simple and compact.

According to another embodiment, the conductive segments may be chargedto the same voltage potential and the switches associated with eachconductive segment may be coupled to opposite ones of the transmissionlines in an alternating fashion. In this arrangement, the switches maybe closed by any stimulation technique to produce a pulse train.According to one embodiment, the apparatus functions by sequentiallyactivating switches from back to front along the pairs of transmissionlines, thereby discharging the segments (each charged to a selectedvoltage) in series into the continuous transmission lines. Appropriatetiming of the closing of the switches is used to create a microwavesignal, a pulse train, having high power and high frequency.

According to still another embodiment, a folded implementation may beused. When the conductive segments have the same polarity, they may becharged together using resistive or other impedance inducing elements toallow simultaneous charging of the conductive segments while effectivelyelectrically isolating each segment during the pulse generation phase.

Still other embodiments include changing the polarity and amount ofcharge placed on each conductive segment, changing the dimensions of theconductive segments relative to one another, placing the conductivesegments in the center between the two transmission lines or in anoffset configuration, changing the delay between switches andintroducing a taper into the transmission lines.

Still other balanced embodiments include introducing a plurality ofgroups of conductive segments between transmission line conductors. Eachgroup is coupled through closing switches to each other or to thetransmission lines in parallel. Each group may be dischargedsimultaneously through groups of closing switches and each successivegroup may be discharged to create a bipolar pulse train.

BRIEF DESCRIPTION OF THE DRAWINGS

The above described features and advantages of the present inventionwill be more fully appreciated with reference to the detaileddescription and appended figures in which.

FIG. 1A depicts a method of generating microwave pulses according to theprior art.

FIG. 1B depicts a schematic of a Blumeline generator according to theprior art.

FIG. 1C depicts two stacked Blumeline generators according to the priorart.

FIG. 2 depicts an embodiment of the present invention implementingtransmission line segments having alternating polarity and equal timedelay τ.

FIG. 3 depicts a generating pulse train produced by transmission linestructures according to an embodiment of the present invention.

FIG. 4 depicts an embodiment of the present invention wherein thesegments are charged to the same polarity and have equal time delay τ.

FIG. 5 depicts an embodiment of the present invention wherein theapparatus is folded into a compact arrangement.

FIG. 6 depicts an embodiment of the present invention where thetransmission line segments are tapered relative to one another.

FIG. 7 depicts an embodiment of the present invention illustrating theplacement of the central conductors relative to the transmission lineconductors.

FIG. 8A depicts an embodiment of the present invention illustrating ablock diagram of a digital synthesis transmission line structure with aload on the operative end.

FIG. 8B depicts an embodiment of the present invention illustrating ablock diagram of a digital synthesis transmission line structure with aload on the operative end and the near end.

FIG. 9 depicts an embodiment of the present invention wherein thetransmission line structure is stacked and shares a common centralconductor.

FIG. 10 depicts an embodiment of the present invention with alternatingcharging at segments, and wherein the transmission line structure has abalanced configuration without a central conductor with alternatingcharging of adjacent segments.

FIG. 11 depicts another embodiment of the present invention wherein thetransmission line structure includes different positioned switcheswithout a central conductor.

FIG. 12 depicts still another embodiment of the present invention withthe same polarity of adjacent segments, wherein the transmission linestructure includes different positioned switches without a centralconductor.

FIG. 13 depicts another embodiment of the present invention wherein thetransmission line structure includes different positioned switches.

FIG. 14 depicts another embodiment of the present invention wherein thetransmission line structure includes different positioned switches.

FIG. 15 depicts another embodiment of the present invention, wherein theseries connected switches are replaced by single switches.

FIG. 16 depicts another embodiment of the present invention, whereinonly one stage of FIG. 15 is shown.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, conductor segments are positionedwithin a three conductor transmission line in order to generatemicrowave pulses. This allows the conductor segments to be switchablycoupled to one or the other of the transmission lines in parallel. Thus,unlike the prior art, microwave pulses are induced from a series ofconductive segments into uninterrupted transmission lines which carrythe signal in a desired direction. The signal does not have to propagatethrough more than one closed switch, and thus longer and more powerfulpulse trains may be produced. This arrangement is susceptible tomultiple implementations.

FIG. 2 depicts a digital synthesis transmission line structure 200 thatgenerates microwave pulses according to an embodiment of the presentinvention. Referring to FIG. 2, the digital synthesis transmission line200 includes two conductors 205 and 210 on either side of a plurality ofcenter transmission line segments (conductors) 220. These segments formtwo conductor transmission line sections with conductors 205 and 210,respectively.

The first conductive or central segment is charged to a differentvoltage than the adjacent central segments 220 relative to surroundingconductors 205 and 210. The first segment 220 has a positive chargerelative to the surrounding conductors 205 and 210. Adjacent centralsegments 220 have opposite polarity. Thus, for example, adjacent centersegments may be charged as a series to +V, −V, +V, −V, as shown. Thestructure 200 further comprises switches 215 that couple each centersegment 220 to the conductor 210.

During operation, each of the switches 215 is closed in a desiredsequence. The discharge of each center segment 220 generates a wave inthe transmission line with conductors 205 and 210, which predominantlytravels to the right. (A fraction also travels to the left as discussedbelow). The voltage generated by discharging the first center segment220, shown as (1), travels only to the right.

Referring to FIG. 2, as the pulse travels to the right in thetransmission lines (205 and 210) from the closing of the first switchshown as (1), it passes the beginning of the second central segment, andthe switch shown as (2) is closed, and the second center segment 220,which is charged negatively, is discharged through switch (2) into thetransmission lines (205 and 210). This produces a similar pulsetraveling to the right. However, the pulse has the opposite polaritywhen compared to the pulse induced by the first segment, and some energytravels backward along the transmission lines. The backward flow ofenergy in the transmission lines formed by conductors 205, 210 and thesecond segment of 220 is impeded by both impedence mismatch and thepresence of the still closed first switch of the first segment 220,which results in small reduction in forward energy flow. Switches (3)and (4) are also closed one after the other when the pulse train passeseach respective switch.

Using the structure of FIG. 2, a train of pulses having alternatingpolarities is produced. The number of pulses is determined by number ofconductive segments and corresponding switches. The width and height ofthe pulses may be varied by varying the geometry of the center segmentrelative to the conductors 205 and 210, the dielectric constant ofmaterial within the transmission line structure, and the distance of thecentral conductor segment from the upper and lower surfaces 205 and 210,among other variations. As discussed further below, other factorsaffecting the waveform produced by the structure 200, which arecontrollable to produce a desired effect, include the amount of chargeplaced on each segment (center conductor 220) and the timing of turningon (closing) each of the switches 215.

FIG. 3 depicts a sample of ideal bipolar pulses in a train waveformproduced and traveling to the right by a structure such as that shown inFIG. 2. Some distortions of a pulse train due to reflections for pulses#2, 3, 4, etc. are not shown. Referring to FIG. 3, the amplitude of thebipolar pulse is +V and −V. The width of each polarity pulse is 2τ,where τ is the transit time along the length of the line formed by aconductive segment. When the conductive segments are spaced immediatelynext to each other, and there is no space in time between positive andnegative pulses, it generally takes 3τ from the closing of a switch forthe pulse to pass the beginning of the next conductive segment andclosing the next switch. By closing the switches (1), (2), (3), (4) in3τ increments, the ideal pulse train as shown in FIG. 3 is created inthe main direction. The quality of this train (which is slightlydistorted by reflected pulses traveling to the left at the beginning)can be improved by using two loads, as shown in FIG. 8B with matchedback-side loads.

FIG. 4 depicts a transmission line structure 250 according to an anotherembodiment of the present invention. Referring to FIG. 4, transmissionline conductors (255 and 260) surround a plurality of center segments265. However, unlike FIG. 2, all of the center segments 265 in FIG. 4are charged to the same polarity and every other center segment 265 iscoupled through a switch 270 to a respective one of the transmissionline conductors 255 or 260 as shown.

In this arrangement, during operation, the switches 270 may be closed byany stimulation technique, generally as indicated by the sequence (1),(2), (3) and (4), as described above, to produce a desired pulse trainhaving pulses that travel to the right, with some energy losses whentraveling in the backward direction. Even though the center segments areall charged to the same voltage polarity, the effect of dischargingalternately into the upper and lower transmission line conductors 255and 260, respectively, creates a train of pulses having alternatepolarities. The wave form of the pulse train is the same as in FIG. 3.Improvement could be achieved in the presence of a back-side load.

FIG. 5 depicts a transmission line structure 275 having a foldedarrangement. The folded geometry allows for increased compactness bypermitting stacking of conductors. Referring to FIG. 5, the structure275 incorporates transmission lines with two conductors 280 and 285 andrespective interdigitated fingers 290 and 292 as shown. Central segmentsare placed between the transmission line conductors 280 and 285 in therecesses between the interdigitated fingers. In particular, a series ofcentral conductors 293 are positioned at a desired distance from thetransmission line fingers 290 and 292. Each central conductor 293 iscoupled to the transmission line conductors 280 through a respectiveswitch 296. Similarly, each central conductor 295 is coupled to thetransmission line conductor 285 through a respective switch 294.

The central segments of the FIG. 5 scheme, being charged to the samepotential and coupled to alternating transmission line conductors 280and 285, through closing switches, thus resembles and operates the sameas the structure of FIG. 4. Accordingly, during operation, the switchesare closed in series (1), (2), (3), (4), (5) to produce a train ofpulses in transmission lines 280 and 285.

The switches 293 and 295 may be implemented as any type of switchaccording to ordinary design considerations. Because the switches arenot placed in series, however, the switches may have a lower on orclosed resistance relative to those required by prior art techniques andthus they may be less expensive or fancy depending on the application.For high power or performance applications, high performance switchesmay be desired. When the switches 293 and 295 are implemented asphotoconductive switches in the folded configuration, and theconfigurations shown in FIG. 2 and FIG. 3, the switches may be embeddedwithin the structure.

According to one embodiment of the present invention, at least a portionof at least one of the transmission lines within the transmission linestructures may be implemented as a mesh structure that has sufficienttransparency to allow laser light to be applied from outside thestructure to a photoconducting switch within the structure. Whenphotoconducting switches are implemented, the switches may be stimulatedby applied light to produce microwave pulse trains.

FIG. 6 depicts a transmission line structure 400 according to stillanother embodiment of the present invention. Referring to FIG. 6, thestructure 400 includes transmission line conductors 405 and 410 that aretapered. In particular, beginning on the left, the conductors are spacedrelatively closely.

The structure 400 may be implemented using any of the techniques shownherein, including those shown in FIGS. 2-4. Referring to FIG. 6, thestructure 400 includes central conductive segments that are positionedbetween the conductors 405 and 410. The central conductive segments arecoupled, respectively, through switches 415 to the lower conductor 410.The switches may be switched in the sequence shown (1) (2) (3) (4) tocreate a pulse train that travel to the right along the transmissionline structure 400.

The advantage of the taper is that at high frequencies and power levels,the conductors themselves become an impediment to efficient operation ofthe structure for generating signals. The taper tends to reduce theeffect of conductor losses, particularly for the segments that arefurthest away from the right end of the structure 400. The taper may beintroduced in the section of the transmission line where the switchesare implemented, or may be introduced on either end of the section withthe switches.

FIG. 7 depicts an illustration of the positioning of central conductorsegments relative to outer transmission lines according to still anotherembodiment of the present invention. Referring to FIG. 7, a digitalsynthesis transmission line structure 500 is shown as having outertransmission line conductors 505 and 510, respectively, and centralconductive segments 515. According to one embodiment of the invention,applicable to any of the transmission line structures shown herein,including those shown in FIGS. 2, 4-6, the distance at which the centralconductive segment 515 is situated relative to the lower conductor 510(D2) and the upper conductor 505 (D1) may be set at any convenientvalue. In some embodiments it may be desirable to have D1=D2. In otherembodiments it may be desirable to have D1>D2 or vice versa. Any ratioof D1 to D2 is contemplated by the applicants and this ratio givesdesigners of digital synthesis transmission line structures anadditional degree of freedom for design alternatives.

These techniques may be used to alter the amount of charge induced byeach segment to configure the pulse amplitude and shape.

FIGS. 8A and 8B depicts an illustrative digital synthesis transmissionline structure 600 showing different load termination options. Thestructure 600 may be any of those depicted in FIGS. 2, 4-7. Referring toFIG. 8A, it is apparent that the structure 600 may be terminated with aload 610 only at the right end. This load may be, for example, aradiator or antenna that presents a matched impedance to thetransmission line structure 600. In a matched impedence scenario, theradiator or antenna does not produce reflections back into the structureand may be used to transmit the pulse train produced by the digitalsynthesis transmission line structure with high efficiency.

FIG. 8B depicts an illustrative digital synthesis transmission linestructure 600 with load terminations 610 and 620, respectively, ateither end. The structure 600 may be any of those depicted in FIGS. 2,4-7. Referring to FIG. 6B, it is apparent that the structure 600 may beterminated with a load at both ends. These loads may be, for example,radiators or antennas that present a matched impedance to thetransmission line structure 600 that does not produce reflections backinto the structure and that may be used to transmit the pulse trainsproduced by the digital synthesis transmission line structure with highefficiency.

The back-side load 620 may be present a matched impedance to thetransmission line and may be used to eliminate reflections of signalstraveling from the right to the left in the digital synthesistransmission line structure, thus making the pulse train traveling fromleft to right more pure. In some embodiments, it may be desirable toomit load 620 to produce a more efficient output of energy from thestructure. In other embodiments, the characteristics desired for theoutput signal may dictate using a matched or mismatched load 620. Instill other embodiments, the load 620 may be a radiator which providesthe ability to generate and propagate signals out of both ends of thestructure 600.

FIG. 9 depicts an example of stacked transmission line structures 900according to another embodiment of the present invention. Referring toFIG. 9, two transmission line conductors 905 and 925 share a commoncentral conductor 910. A plurality of center conductors segments 910 arepositioned between conductors 905 and 915. Similarly, a plurality ofcenter conductor segments 920 are positioned between conductors 915 and925. There may be symmetry between the upper and lower portions of thestructure 900 such that pairs of center conductors 910 and 920 arepositioned at the same location along the transmission line structure900 relative to one another that may be discharged simultaneouslythrough respective closing switches.

Each of the center segments are charged to the same potential (V)relative to the surrounding central conductor 915 and outer conductors905. This eliminates static voltages between adjacent conductors. Eachsuccessive center segment, however, is alternatively coupled to thecentral conductor 915 or one of the respective outer conductors 905 or925. In this manner, the same potential may be applied to the centersegments, and the center segments may nonetheless generate bipolarpulses as previously discussed with respect to FIG. 3.

During operation, the center segments 910 and 920 in vertical alignmentshould be switched together at the same time. All other segments invertical alignment should be switched at the same predetermined time.Pairs of switches may be closed in the sequence (1), (2), (3) and (4),to discharge the respective center segments to produce a pulse trainthat travels from the left to the right along the conductors 905 and925. Arrows on FIG. 9 indicate the direction of current produced byclosing the switches (1). For a second sequence of switches (2), thecurrent will flow in the opposite direction. Any of the techniques forpositioning, charging and switching the conductive segments describedherein may be applied to the embodiment shown in FIG. 9 and FIGS. 10-15.With respect to FIG. 9, the discharge of the center segments producesvoltages that are additive from each pair of center segments.Accordingly, the amplitude of the pulse train produced is +2V and −2V.

FIG. 10 depicts a transmission line structure 1000 according to anotherembodiment of the invention. The structure of FIG. 10 includestransmission line conductors 1005 and 1020 and a series of centralsegment pairs 1010 and 1015 between the conductors 1005 and 1020. In thestructure 1000 as in the structure of FIG. 9 there are central segmentpairs, each of which is switched simultaneously. The main differencebetween the structures 900 and 1000 is that the structure 1000 does nothave a central conductor. This structure can be obtained as acombination of two identical structures shown in FIG. 2, one of which isreversed (flipped vertically). In this case, the common, centraltransmission line conductor may be eliminated. In addition, in thestructure 1000, each of the central segments 1010 and 1015 are coupledtogether, rather than to one of the outer conductors, through arespective closing switches. This simplifies charging of the segments.

Each upper center segment is charged to +2V or −2V relative to the lowercenter segment in an alternating manner between adjacent pairs of centersegments. Each center segment is similarly charged relative to the outertransmission line conductors which may be at ground potential.

During operation, the switches may be closed in the sequence shown (1),(2), (3), (4) to create a train of pulses that are transmitted along thetransmission line conductors 1005 and 1020 to the load, which is 4Z₀.The amplitude of the signal is +2V and −2V. The structure 1000 is moreefficient than the structure 900 because there is no center conductorand therefore no losses due to canceling currents. The results indecreasing losses by approximately 25%. Besides which, the design ofFIG. 10 is simpler than the stacked configuration FIG. 11 depicts atransmission line structure 1100 according to another embodiment of theinvention. The structure of FIG. 11 includes transmission lineconductors 1105 and 1120 and a series of central conductive segmentpairs 1110 and 1115. The structure 1100 is similar to the structure 1000shown in FIG. 10 in the sense that there are central segment pairsbetween the outer conductors and each central segment pair is switchedsimultaneously. The main difference between the structures 1100 and 1000is that in the structure 1100, the center segments are coupled to theouter conductors through closing switches rather than to each other. Forexample, all of the center segments 1110 are coupled to the uppertransmission line conductor 1105 through closing switches and all of thecenter segments 1115 are coupled to the lower transmission lineconductor 1120.

During operation, the switches are closed sequentially as shown (1),(2), (3), (4), voltage of alternating potential is induced in the outerconductors thus creating a pulse train in the outer transmission lineconductors 1105 and 1120. The pulse train is produced in a manneranalogous to that shown in FIG. 2. However, the amplitude is +2V, −2V.The efficiency of the structure depicted in FIG. 11 is the same as thatdepicted in FIG. 10.

FIG. 12 depicts a transmission line structure 1200 according to anotherembodiment of the invention. The structure of FIG. 12 includestransmission line conductors 1205 and 1220 and a series of centralconductive segment pairs 1210 and 1215. The structure 1200 is similar tothe structures of FIGS. 10 and 11 in the sense that there are centralsegment pairs between the outer conductors and each central segment pairis switched simultaneously. The main difference between the structure1200 of FIG. 12 and those shown in FIGS. 10 and 11 is that in thestructure 1200, adjacent pairs of center segments are coupleddifferently using the closing switches so that one pair is coupledtogether and the adjacent pair is coupled to the outer conductors. Bycontrast, in FIG. 10 the center segments are always coupled together andin FIG. 11 the center segments are coupled to the outer conductors. Thisdifference is because all upper segments have the same polarity, whichis opposite that of all lower segments. FIG. 12 is thus a combination oftwo structures shown in FIG. 4 after eliminating the center conductor.

During operation, the switches are closed sequentially as shown (1),(2), (3), (4), voltage of alternating potential is induced in the outerconductors thus creating a pulse train in the outer transmission lineconductors 1205 and 1220. The pulse train is produced in a manneranalogous to that shown in FIG. 3 for a positive starting pulse.However, the amplitude is +2V, −2V. The efficiency of the structuredepicted in FIG. 11 is the same as that depicted in FIG. 10 and FIG. 11.

FIG. 13 depicts a transmission line structure 1300 according to anotherembodiment of the invention. The structure of FIG. 13 includestransmission line conductors 1305 and 1325 and a series of internalconductive segment triplets 1310, 1315 and 1320. The structure 1300 issimilar to the structures of FIG. 10-12 in the sense that there areinternal segment groups between the outer conductors 1305 and 1325 andeach internal segment group is switched simultaneously. The maindifference between the structure 1300 of FIG. 13 and those shown inFIGS. 10-12 is that in the structure 1300, the internal segments aregrouped in triplets and adjacent triplets of center segments are coupleddifferently using the closing switches so that one pair of conductors inthe triplet is coupled together through closing switches and theremaining center segment is coupled to a respective one of the outerconductors. Specifically, adjacent center segments 1310 are coupledthrough closing switches in an alternating manner to the outer conductor1305 or the center segment 1315. Adjacent center segments 1315 arecoupled through closing switches in an alternating manner to the centersegments 1310 or the center segments 1320. Adjacent center segments 1325are coupled through closing switches in an alternating manner to thecenter segments 1315 or to the outer conductor 1325. The center segments1310 are charged to +V, relative to transmission line conductor 1305.The center segments 1315 are charged to −2V, relative to segments 1310and 1320. Segments 1320 are charged to +V, relative to transmission lineconductor 1325.

During operation, the switches are closed sequentially as shown (1),(2), (3), (4), voltage of alternating potential is induced in the outerconductors thus creating a pulse train in the outer transmission lineconductors 1305 and 1325. The pulse train produced resembles that shownin FIG. 3. However, the amplitude is +3V, −3V.

The structure 1300 is an alternative to the stacked structure similar toFIG. 8 with three stacked structures similar to FIG. 4. The losses inthe structure 1300 will be 33% lower, due to the elimination of twointermediate conductors with two oppositely directed currents on eachconductor.

FIG. 14 depicts another embodiment, a double balanced implementation ofthe structure shown in FIG. 11. When compared with the stacked structure(extending FIG. 9) three internal strip conductors with currents on eachof each conductor are eliminated. This simplifies the structure andprovides 37.5% lower loses compared to four stacked structures of FIG. 2or FIG. 4. Based on the combinations of structures illustrated in FIGS.10 through 14, it is apparent that other balanced circuits andstructures may be presented. While particular embodiments of the presentinvention have been described, it will be understood by those havingordinary skill in the art that changes may be made to those embodimentswithout departing from the spirit and scope of the invention.

FIG. 15 depicts another embodiment, similar to FIG. 13 in the structureof the transmission lines, wherein each pair of series connectedswitches is replaced by a single switch. In some cases, when the voltageon the switches is not a primary limitation, such a structure with alower number of switches is preferable.

Similarly, the number of switches can be reduced in the structuresdepicted in FIGS. 10, 12, and 13.

All of the above discussion relating to FIGS. 10-15 is applicableindependent of the number of vertical strips that define the number ofgenerated pulses. Increasing the number of segments in each verticalalignment increases the power in the pulse.

In FIG. 16, where only one stage is used, this will improved thestructure of stacked Blumeline generators by reducing the number ofconductors and switches.

1. An apparatus for generating a plurality of electrical impulses,comprising: two transmission line conductors; a plurality of groups ofconductive segments interposed between and electrically isolated fromthe two transmission lines, the segments capable of being charged;wherein each segment is operatively connected through a switch todischarge the conductive segments to create a microwave signal on thetransmission lines.
 2. The apparatus according to claim 1, wherein theplurality of groups comprises pairs of conductive segments.
 3. Theapparatus according to claim 2, wherein each conductive segment withineach pair of conductive segments is charged to a different voltagepotential relative to one another.
 4. The apparatus according to claim2, wherein each conductive segment within each pair of conductivesegments is charged to the same voltage potential relative to oneanother.
 5. The apparatus according to claim 2, wherein adjacent pairsof conductive segments are charged to a different voltage potentialrelative each other.
 6. The apparatus according to claim 2, whereinwithin each pair of conductive segments, upper conductive segments areall coupled to an upper one of the transmission line conductors throughthe switches and lower conductive segments are coupled to a lower one ofthe transmission line conductors through the switches.
 7. The apparatusaccording to claim 2, wherein within each pair of conductive segments,upper conductive segments are all coupled to lower conductive segmentsthrough the switches.
 8. The apparatus according to claim 2, whereinadjacent pairs of the conductive segments are coupled, respectively, tothe outer transmission line conductors for one pair and to each otherfor the adjacent pair.
 9. The apparatus according to claim 1, whereinthe groups of center segments comprise triplets of conductive segments.10. The apparatus according to claim 9, wherein the center segment ofeach triplet is charged to the same voltage potential through theswitches.
 11. The apparatus according to claim 10, wherein the centersegment of each triplet is coupled to one of the other two segments ofeach triplet through the switches.
 12. The apparatus according to claim1, wherein the switches are optically activated.
 13. The apparatusaccording to claim 1, wherein the transmission lines are coupled to aload on an operative end.
 14. The apparatus of claim 13, wherein theload is an adiabatic transformer.
 15. The apparatus of claim 1, whereinthe segments are operatively connected via the switches to alternatingsides of the transmission lines.
 16. A method of generating microwavesignals, comprising: closing a first group of switches to discharge afirst group of central segments into transmission line conductors;closing a second group of switches to discharge a second group ofcentral segments into transmission line conductors after a period ofdelay in order to create, together with the closing of the first groupof switches, a bipolar pulse.
 17. The method of claim 16, wherein theclosing of the second group of switches occurs after the closing of thefirst group of switches by an amount determined to allow a wavegenerated in the transmission line conductors by the second group ofswitches to join the tail of a wave generated in the transmission lineconductors by the first group of switches.
 18. The method of claim 17,wherein the amount is approximately 3τ where τ is the transit time alongof a length of each central segment.